The present invention generally relates to a method and system for inerting aircraft fuel tanks by providing a nitrogen enriched air supply, and specifically to a system for increasing working air pressures to optimize efficiency of an air separation module by using exhaust gases to power a second compressor.
It is recognized that fuel vapors created within fuel tanks become combustible in the presence of oxygen. The possibility of explosion or fire can be substantially reduced by reducing or eliminating the amount of oxygen present within the fuel tank. It is known in the art to equip aircraft with onboard inert gas generating systems. The inert gas generating system supplies nitrogen enriched air to the vapor space within the fuel tank. The nitrogen-enriched air has a substantially reduced oxygen content that reduces or eliminates combustible conditions within the fuel tank.
Typically, the inert gas generating system includes a compressor powered by a motor that draws in air at a first pressure and exhausts air at a second pressure. The second pressure being much higher than the first pressure in order to obtain an optimal working pressure required for an air separation module. It is understood by workers in the art that air separation modules operate most efficiently at elevated pressures above pressure typically available from other on board systems. Therefore, a compressor elevates the pressure of air to the air separation module. The compressor and motor to drive the compressor contribute a substantial amount of weight to an aircraft. Weight and space on an aircraft are at a premium and any reduction or increase has a substantial effect on aircraft operation.
Accordingly, it is desirable to develop an inerting system for producing inert gas on board an aircraft that obtain optimal working pressures for air separation modules while reducing overall system weight and size.